A new study by automotive industry analyst Polk says that 38.5 percent of all new vehicle registrations in the United States are attributed to women. That's up 2.5 percent compared to 2006. The number of women buying new vehicles in the U.S. has been on a rising path in the past four years.  Peters of Nashua offers 3 of the 5 top five brands based on women's share of brand sales - and 2 of the top 5 brands based on passenger vehicles sales to women - placing Nissan among the top five brands chosen by women. Citing fuel efficiency as a top reason women buy, Nissan offers a great choice - with 8 models that get 30 or more highway miles to the gallon. [Source: Polk,TruCar, Nissanusa.com ]